Magnetic position sensing involves the use of a magnetic sensor to provide an indication of the angular position of a rotatable magnetic field. One existing type of magnetic field sensor is an anisotropic magnetoresistive (AMR) sensor. An AMR sensor may include resistive elements that are configured into one or more Wheatstone bridge configurations. Each of the resistive elements may have a resistance that varies according to the magnitude and/or direction of a magnetic field that is incident upon the respective resistive element. The Wheatstone bridge configuration may generate an output voltage value that is indicative of the change in resistance caused by the amplitude and direction of the magnetic field.
Some types of AMR devices are configured to generate a unique output voltage value for rotational angles of an incident magnetic field within a range of 180 degrees. For example, an AMR device may include two Wheatstone bridge configurations oriented 45 degrees in rotation from each other. The resistive elements within the Wheatstone bridge configurations may be formed from Permalloy material. In such examples, the resistance of each of the resistive elements may vary according to a cos2(θ) relationship where θ is the angle between the magnetic moment vector of the resistive element and the current flowing through the resistive element. Such an AMR device may be able to produce a first output voltage that varies according to a sin(2θ) relationship and a second output voltage that varies according to a cos(2θ) relationship. The first and second output voltages may be used to determine an angular position of a magnetic field incident on the AMR device. Because the sin(2θ) function and the cos(2θ) function are periodic functions each with a period of 180 degrees, such an AMR device is not able to provide a unique output voltage value for each rotational angle of an incident magnetic field within a range of 360 degrees.